PDF file has its own bookmark function. The bookmark can be added at the page being read by the readers, so that the readers can skip to the page by clicking on the bookmark in the next reading, instead of searching from the start page, which provides readers convenience to a certain extent. However, in the prior art, the readers can only mark the reading pages by bookmarks, but cannot mark different location in the same page. Thus readers can only read and search from the first line of the marked page after skip to the marked page. It is really a time-consuming and effortless matter for the people with visual impairment. Therefore, it is really a problem to be solved urgently for those skilled in the art to provide a method that not only can recognize different page, but also can identify different content on the same page, so as to directly position at the specific location in a page when adding a bookmark.